An extension ladder has an upper and lower ladder portion which slide with respect to each other to adjust the height of the ladder. Each portion has two long parallel structural members, sides, or legs, which are coupled by equally spaced parallel rungs. Along the bottom of the two legs of the lower ladder portion are often swivel feet which pivot as needed such that the ladder may rest at an angle against a structure, such as tilted against the exterior of a home, building, or part thereof.
Typically, the upper ladder portion is extended with respect to the lower ladder portion by a user pulling on a rope attached near the bottom of the upper ladder portion which is fed through a pulley attached near the top of the lower ladder portion. The extension of the ladder typically occurs with the top of the ladder extending in the air and not leaning on any surface which could hinder sliding of the upper ladder portion with respect to the lower ladder portion. When the top of the upper portion of the ladder is at a desired position, a locking mechanism engages between the two ladder portions to enable safe climbing of the ladder, and the ladder is tilted to rest at an angle against the structure to be climbed.
For safe use of the extension ladder, the ladder is used on level or substantially level surfaces. If the surface is not substantially level, such as on a hill, steps, or any uneven surface which cannot evenly support the two legs of the extension ladder, safe use of the ladder is a problem. To address this problem, ladder levelers have been proposed which are either attached to one of the legs to extend the leg, such as shown for example in U.S. Pat. No. 3,933,222 to Craig, Jr., or attached to rungs adjacent to or near one leg of the two ladder's legs to effectively extending that leg, such as shown in U.S. Pat. No. 4,984,655, to Scherer et al., or U.S. Pat. No. 5,121,813 to Funston, or attached to both one of the ladder's legs and its rungs, such as shown in U.S. Pat. No. 5,174,412 to Vega. Other ladder levelers proposed have two separate devices each attached to one of the ladder's legs and are adjustable in length, such as shown in U.S. Pat. No. 6,435,306, to Stoneburg. A further more complicated ladder leveler is described in U.S. Pat. No. 6,378,656 to Kohler, which has a single unit attached to the bottom of both of the ladder's legs, and has two pivotal arms which lie on a surface.
In all of these ladder leveler devices, the ladder combined with the leveler device distributes the weight of the ladder down both of the ladder's legs to the ground, or other surface, via the ladder leveler device. Moreover, in most ladder leveler devices the devices need to be readjusted (e.g., in height) for use with the same ladder on different uneven surfaces, or removed from the ladder to enable use of the ladder on level surfaces. When a ladder leveler device is not present or not desired, holes are sometimes dug in a surface if possible, as in the case of a dirt or loose ground surface, to support one or both ladder legs, or block(s) of wood or other rigid material are sometimes placed under one or both ladder legs, to enables the feet of the ladder to be substantially level. However, these block(s) or leg(s) in dug holes can shift during ladder use creating a safety hazard to a climber on the ladder, and/or require another person to hold onto the ladder when used. Thus, a device easily attachable to an extension ladder, which is not a ladder leveler, is not complex, and enables the ladder to be used on level and non-level surfaces without modification (such as height adjustment) or removal of the device would be desirable.